I just accidentally discovered that you can zoom in Excel via keyboard and mouse. If you hold down both the Control and Option keys, and then scroll using the mouse (for me it is two fingers on the MacBook Pro's track pad), you'll change the zoom level on the Excel sheet. I tried the same on Word but it does not work. I tried also on other apps but with no success.

[robg adds: To zoom in Word via the scroll wheel, hold Command and Control, then scroll your mouse. (This older hint indicated that Word would zoom with Control and scroll, but that function has been taken over by the OS now for system-wide zooming.) Note that in both Excel and Word, at least on my machine, the scroll wheel is very sensitive, so you'll want to use small motions.]

Thanks for both of these hints! This solves an almost daily problem I had with Word and the occasional need to zoom in temporarily. (I'm actually kind of embarrassed that I didn't know these already....)

You genius. I have just migrated from Windows, where this has long been a key Office feature. I'd found the Mac OS zoom, but wanted my document zoom back - and is this documented anywhere or in the Office help? Of course not! Thanks